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Abstract

A snapshot 3-Dimensional Optical Coherence Tomography system was developed using Image Mapping
Spectrometry. This system can give depth information (Z) at different spatial positions (XY) within
one camera integration time to potentially reduce motion artifact and enhance throughput. The
current (x,y,λ) datacube of (85×356×117) provides a 3D
visualization of sample with 400 μm depth and 13.4
μm in transverse resolution. Axial resolution of 16.0
μm can also be achieved in this proof-of-concept system. We present an
analysis of the theoretical constraints which will guide development of future systems with
increased imaging depth and improved axial and lateral resolutions.

Figures (12)

The concept of combining Full-field OCT (FF-OCT) and IMS systems to develop snapshot 3D-OCT. A
low coherence source travels to both sample and reference arms. Back-scattered light creates
interference and is fed into the the IMS system. The mapper slices the image and regroups different
regions into separate pupils. A large camera captures spectral and spatial data imaged by a lenslet
array.

Image mapper fabrication. (a): Mapper in fabrication. The substrate is mounted on
the Nanotech milling machine. Two tools are placed on spindle prior to cutting facets.
(b): Reflection of ruler’s straight edge on the finished mapper.
(c): Mapper looking from the top. Different facet tilts are shown as variations in
depth of cuts. (d): Examination of mapper’s facets with white-light
interferometer. (e): Mapper looking from the front. (f): Enlarged section
of mapper looking from the front showing finer cuts for individual facets.

Mapper facet and pupil distribution. (a): Facet tilt directions relative to mapper.
(b): Pupil distribution from one block of mapper (100 facets). Facets whose numbers are
not shown are discarded in the leftmost and rightmost columns. (c): Grouping and order
of facets. Facet of the same y-tilt correspond to light grouped in the same row; and those of the
same x-tilt correspond to the same columns. Thus two facets which are 100 facets apart have the
exact same x and y tilts.

OCT calibration steps. a: A segment of a raw sub-image with horizontal features from sample and
vertical interferometric fringes. b: One spectral cross-section taken from (a). c: Calibrated
spectra corresponding to the raw image in (a). Spectra along the facets form a gradient from black
(610 nm) to white (640 nm). d: The initial wavelength-pixel relationship is fitted to a third-order
polynomial. e: The calibrated wavelength after zero-padding to 512 data points to prepare for depth
reconstruction. f: A spectrum of inteferometric fringes with DC components removed. g: Depth profile
reconstructed from the fringes shown in f. h: Relationship between wavelengths and the array
indices. For a narrow spectral band such as that used here, this relationship is almost linear.

Snapshot 3D-OCT system’s depth assessment. a: Different depth positions of a flat,
reflecting mirror mounted on a translation stage. b: Measured axial resolution from one
representative transverse location. c: Relationship between peak pixel position and mirror physical
position. Note that at the position around 400 μm, peak positions become
undetectable, indicating the end of the imaging depth. d: Linear regression of the relationship
between peak pixel position and mirror position.

System evaluation with simple 3D structural sample. a: A 2D image of an US dime taken with
reference camera. b: Corresponding transverse surface acquired with snapshot 3D-OCT system. c:
Transverse surfaces at different depths. d: Cross-sections along the depth range.

3D snapshot of a layer of onion placed on top of a highly scattering metal surface. a: Image of a
layer of onion (bottom) on a metal surface (top) acquired with the reference camera. b: Transverse
surface acquired with snapshot 3D-OCT system. c: Representative transverse sections at different (z)
depths.